1. Field of the Invention
The present invention relates to the art of producing synthetic antibiotics and specifically to a process for an improved synthesis of cephem lactones, i.e. a group of compounds known to be of value in the synthesis of cephalosporin-type antibiotics.
2. Description of the Prior Art
Certain cephem lactones have been disclosed in British patent specification No. 948,076 and in the Monography by E. H. Flynn, "Cephalosporins and Penicillins," New York, 1972. A recent review of the state of the art in the field of synthetic antibiotics by P. G. Sammes has been published in Chem. Reviews, 1976, Vol. 76, No. 1, pages 113 to 155. The Sammes review includes, inter alia, a detailed discussion of various syntheses of cephem and cephalosporin type antibiotics and some of the methods involved have become known as Woodward Approach, Roussel-Squibb Route, etc.
It has been recognized for some time that the cephem lactones exhibit antibiotic, or antibacterial, properties, c.f. Journ. Am. Chem. Soc. 84, page 3401 (1962) but, at present, the cephem lactones are of primary importance for production of the corresponding carboxylic acids, i.e. the "classical" antibiotics. For example, the Roussel-Squibb Route, the Beecham Method and the Syntex Approach referred to in the above mentioned review by Sammes include the use of cephem lactones as intermediate components. However, the actual cephem lactone syntheses involved have some severe draw-backs for commercial production as they suffer from one or more of the following disadvantages:
(a) The starting materials used are costly or difficult to produce; PA1 (b) the yields of the target cephem lactones are low; PA1 (c) the end product is racemic.
Thus, it is a main object of the present invention to provide for a cephem lactone synthesis that is improved with regard to one or more of the above noted defects of prior art methods.
Other objects of the invention are novel intermediates suitable for cephem lactone syntheses, and certain novel and valuable stereisomers of such cephem lactones.
Further objects of the invention will become apparent as the specification proceeds.